Measures of Mitochondria Dysfunction in PD

Inclusion Criteria: * Age 65-85 years. * Ability to attend a 3-hour study visit in Seattle, WA. * Ability to read and speak English. * Hoehn \& Yahr Stage 2-3. (bilateral disease, not severely disabled.) Exclusion Criteria: * Any contra-indication to magnetic resonance imaging * A history of epilepsy, stroke, brain surgery, or structural brain disease. * The presence of other serious illnesses * Current or recent enrollment in a clinical trial involving an investigational product or device. * Supplementation with NAD, nicotinamide mononucleotide (NMN), nicotinamide riboside (NR), and other nutraceuticals designed to target NAD for 30 days prior to baseline study visit. * Current drug or alcohol use or dependence. * Inability/unwillingness to provide informed consent. (e.g. diagnosis of dementia, confusion about study goals or participation.) * Acute infection (e.g. upper respiratory, dermal) in the previous 30 days. * Right limb tremor or dyskinesia that cannot be comfortably controlled for 90 minutes.